/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.server.ai.mission;

import java.util.logging.Logger;

import javax.xml.stream.XMLStreamException;

import net.sf.freecol.common.io.FreeColXMLReader;
import net.sf.freecol.common.io.FreeColXMLWriter;
import net.sf.freecol.common.model.Colony;
import net.sf.freecol.common.model.Location;
import net.sf.freecol.common.model.Unit;
import net.sf.freecol.common.model.pathfinding.CostDeciders;
import net.sf.freecol.common.util.LogBuilder;
import net.sf.freecol.server.ai.AIColony;
import net.sf.freecol.server.ai.AIMain;
import net.sf.freecol.server.ai.AIUnit;
import net.sf.freecol.server.ai.EuropeanAIPlayer;
import net.sf.freecol.server.ai.GoodsWish;
import net.sf.freecol.server.ai.Wish;
import net.sf.freecol.server.ai.WorkerWish;


/**
 * Mission for realizing a <code>Wish</code>.
 */
public class WishRealizationMission extends Mission
{

    private static final Logger logger = Logger.getLogger( WishRealizationMission.class.getName( ) );

    /** The tag for this mission. */
    private static final String tag = "AI wisher";

    /** The wish to be realized. */
    private Wish wish;


    /**
     * Creates a mission for the given <code>AIUnit</code>.
     *
     * @param aiMain The main AI-object.
     * @param aiUnit The <code>AIUnit</code> this mission is created for.
     * @param wish The <code>Wish</code> which will be realized by
     *     the unit and this mission.
     */
    public WishRealizationMission( AIMain aiMain, AIUnit aiUnit, Wish wish )
    {
        super( aiMain, aiUnit, wish.getDestination( ) );

        this.wish = wish;
        wish.setTransportable( aiUnit );
    }

    /**
     * Creates a new <code>WishRealizationMission</code> and reads the
     * given element.
     *
     * @param aiMain The main AI-object.
     * @param aiUnit The <code>AIUnit</code> this mission is created for.
     * @param xr The input stream containing the XML.
     * @throws XMLStreamException if a problem was encountered
     *      during parsing.
     * @see net.sf.freecol.server.ai.AIObject#readFromXML
     */
    public WishRealizationMission( AIMain aiMain, AIUnit aiUnit,
                                   FreeColXMLReader xr ) throws XMLStreamException
    {
        super( aiMain, aiUnit );

        readFromXML( xr );
    }


    /**
     * Get the wish handled by this mission.
     *
     * @return The mission <code>Wish</code>.
     */
    public Wish getWish( )
    {
        return this.wish;
    }

    /**
     * Why would this mission be invalid with the given AI unit and location?
     *
     * @param aiUnit The <code>AIUnit</code> to check.
     * @param loc The <code>Location</code> to check.
     * @return A reason for invalidity, or null if none found.
     */
    public static String invalidReason( AIUnit aiUnit, Location loc )
    {
        String reason;
        return ( ( reason = invalidAIUnitReason( aiUnit ) ) != null ) ? reason
                : ( ( reason = invalidTargetReason( loc,
                                                    aiUnit.getUnit( ).getOwner( ) ) ) != null ) ? reason
                : null;
    }


    // Implement Mission
    //   Inherit getTransportDestination, isOneTime

    /**
     * {@inheritDoc}
     */
    @Override
    public void dispose( )
    {
        if ( this.wish != null )
        {
            this.wish.setTransportable( null );
            this.wish = null;
        }
        super.dispose( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int getBaseTransportPriority( )
    {
        return NORMAL_TRANSPORT_PRIORITY;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Location getTarget( )
    {
        return ( this.wish == null ) ? null : this.wish.getDestination( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setTarget( Location target )
    {
        // Ignored, target is set by wish
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Location findTarget( )
    {
        return getTarget( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String invalidReason( )
    {
        return ( this.wish == null ) ? "wish-null"
                : invalidReason( getAIUnit( ), getTarget( ) );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Mission doMission( LogBuilder lb )
    {
        lb.add( tag );
        String reason = invalidReason( );
        if ( reason != null ) return lbFail( lb, false, reason );

        // Move towards the target.
        final Unit unit = getUnit( );
        Location target = getTarget( );
        Unit.MoveType mt = travelToTarget( target,
                                           CostDeciders.avoidSettlementsAndBlockingUnits( ), lb );
        switch ( mt )
        {
            case MOVE: // Arrived
                break;

            case MOVE_HIGH_SEAS:
            case MOVE_NO_MOVES:
            case MOVE_NO_REPAIR:
            case MOVE_ILLEGAL:
                return lbWait( lb );

            case MOVE_NO_ACCESS_EMBARK:
            case MOVE_NO_TILE:
                return this;

            default:
                return lbMove( lb, mt );
        }

        lbAt( lb );
        if ( target instanceof Colony )
        {
            final AIMain aiMain = getAIMain( );
            final Colony colony = ( Colony ) target;
            final AIUnit aiUnit = getAIUnit( );
            final AIColony aiColony = aiMain.getAIColony( colony );
            final EuropeanAIPlayer owner = getEuropeanAIPlayer( );
            aiColony.completeWish( wish, unit.toShortString( ), lb );
            // Replace the mission, with a defensive one if this is a
            // military unit or a simple working one if not.
            if ( unit.getType( ).isOffensive( ) )
            {
                if ( owner.getDefendSettlementMission( aiUnit, colony ) != null )
                {
                    lbDone( lb, true, "ready to defend, ", colony );
                }
                else
                {
                    lbFail( lb, true, "unable to defend" );
                }
            }
            else
            {
                aiColony.requestRearrange( );
                if ( owner.getWorkInsideColonyMission( aiUnit, aiColony ) != null )
                {
                    lbDone( lb, true, "ready to work ", colony );
                }
                else
                {
                    lbFail( lb, true, "unable to work" );
                }
            }
        }
        else
        {
            lbFail( lb, true, "broken wish ", wish );
        }

        this.wish = null; // completeWish disposes
        return lbDrop( lb );
    }


    // Serialization

    private static final String WISH_TAG = "wish";
    // @compat 0.10.3
    private static final String OLD_GOODS_WISH_TAG = "GoodsWish";
    // end @compat


    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeAttributes( FreeColXMLWriter xw ) throws XMLStreamException
    {
        super.writeAttributes( xw );

        xw.writeAttribute( WISH_TAG, wish );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void readAttributes( FreeColXMLReader xr ) throws XMLStreamException
    {
        super.readAttributes( xr );

        final AIMain aiMain = getAIMain( );

        final String wid = xr.getAttribute( WISH_TAG, ( String ) null );
        wish = xr.getAttribute( aiMain, WISH_TAG, Wish.class, ( Wish ) null );
        if ( wish == null )
        {
            if ( wid.startsWith( GoodsWish.getXMLElementTagName( ) )
                    // @compat 0.10.3
                    || wid.startsWith( OLD_GOODS_WISH_TAG )
                // end @compat
            )
            {
                wish = new GoodsWish( aiMain, wid );

            }
            else if ( wid.startsWith( WorkerWish.getXMLElementTagName( ) ) )
            {
                wish = new WorkerWish( aiMain, wid );

            }
            else
            {
                throw new XMLStreamException( "Unknown wish tag: " + wid );
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getXMLTagName( ) { return getXMLElementTagName( ); }

    /**
     * Gets the tag name of the root element representing this object.
     *
     * @return The <code>String</code> "wishRealizationMission".
     */
    public static String getXMLElementTagName( )
    {
        return "wishRealizationMission";
    }
}
